It is a recognised fact that most piston engines are inherently inefficient. A number of factors add to this inefficiency including the motion of the pistons, and the fact that to a large extent the piston is either at rest or in a drag state which reduces the effect of the energy available at the engine's crank. Also, a significant amount of energy is required to move the piston to the top of the bore during the compression or pump stroke.
A further cause of inefficiency, in for example existing internal combustion engines, is that there are gears, cams and other equipment necessary to enable the engine to function. This results in reduced efficiency, and in the final analysis only a small percentage of input energy is transferred to the output.
Rotary type engines overcome some of the above problems. However, such engines are complex and there are sealing problems between the moving parts. While they have dramatically changed the design of standard piston and cylinder engines they have resulted in complex sealing and design problems which result in unreliability.
Hybrid type engines are known. One such hybrid, described in EPO964136, is a rotary type configuration with the engine block defining a cylindrical rotor having a plurality of bores which open to combustion chambers near its periphery. A piston is disposed in each bore. Each piston has its own crank with rotation being transferred to the engine block/rotor via a planetary gearbox arrangement. Inlet ports, spark plugs and outlet ports are arranged around the periphery of the engine housing in the same manner as a conventional rotary engine. The claimed advantage of this configuration is that the power/movement of the pistons is almost completely converted to rotational movement of the engine and thus it produces a greater power output per size/weight than a conventional piston engine. A further claimed advantage is that the rotary nature of the engine does away with the need to employ valves and thus the associated problem of valve damage in conventional engines. However, the engine still suffers from considerable sealing problems and losses in the planetary gearbox linking the piston rods to the rotor.
Another hybrid type engine is described in AU 8496/27. This engine is of the type that has a continuously rotating group of cylinders disposed tangentially on a main rotatable member. Corresponding pistons are intermittently rotating. The pistons are attached to piston levers pivoted about the centre of rotation. In order to achieve correct operation of this engine the pistons must be locked against movement in either direction during combustion so that energy can be transferred to the rotatable member via the cylinders. After combustion the piston must accelerate at twice the speed of the rotary member in order to move back to top dead centre for the next combustion stroke. A sophisticated arrangement of gears and levers are required to operate the piston in this manner manner. Because the piston must travel at twice rotational speed the engine's maximum speed is limited by the ability to move the piston from standstill to top dead centre.
As well as the above mentioned disadvantages, in existing piston engines the time the piston spends at the top and bottom of the stroke is very short as the cranksharft operates to change direction at the instant that the extreme of piston travel is reached. This reduces dwell and leads to incomplete burning of gases in combustion. These incompletely burnt gases are expelled in the exhaust resulting in inefficiencies in the engine and pollution of the atmosphere.
Accordingly it is an object of the present invention to provide an engine which is efficient and economical to run. It is a further object of the present invention to provide an engine which has high rotational inertia and torque relative to its size and weight.
It is still a further object of the present invention to provide an engine which may be controlled in a variety of ways to meet a variety of functional needs. Yet a further object of the present invention to provide an engine which ameliorates some of the disadvantages of known engines, or at least provides the public with a useful choice.